1. Field of the Invention
This invention relates to an improved injection molding machine providing a rotary type clamping apparatus for molding of multicolor or multilayer products and more particularly an improved rotation mechanism of rotary table plate on which plural moldhalves are fixed.
2. Referrence to Prior Art
A rotary injection molding machine provides a clamping apparatus of which plural molds are fixed on the rotary table plate for multicolor or multilayer molding and insert molding with the rotary type clamping apparatus of an injection molding machine; the stationary moldhalves with a stationary platen and movable moldhalves with a movable platen are provided and a rotary table plate is provided with either of them.
For molding of multilayer or multicolor products, the following operation is required of the rotary type clamping apparatus, that is, the movable platen is reciprocated to the stationary platen for mold opening and closing, and after moldhalves have been closed, the movable platen is pressed to the stationary platen for clamping the moldhalves. And moreover, rotation of the rotary table plate providing plural male mold halves is required for multi injection molding. For this requirement it is required for the rotary table plate to touch the movable platen closely while clamping the moldhalves and to be apart from the movable platen while rotating. For supplying such requirement, a spline shaft is used to rotate the rotary table plate. But backlash of the spline shaft makes error of stop position of the moldhalves; the larger the radius of the rotary table plate is, the larger the error is.
And also when the rotary table plate rotates, it is required that the rotary table plate is lifted from the movable platen to prevent friction between the rotary table plate and the movable platen and consequently a lifting device of the rotary table plate is needed.